On Thu, Jun 2, 2011 at 2:18 PM, Dag Sverre Seljebotn <d.s.seljebotn@astro.uio.no> wrote:
On 06/02/2011 06:39 PM, Robert Bradshaw wrote:
In looking at merging fused types, it's time to nail down the syntax. The current implementation is
ctypedef cython.fused_type(list, dict, object) fused_t
This requires an addition to the grammer to allow the "call" syntax in a type declaration, as well as special casing to make it allowed only in a typedef. What about
cython.fused_type[list, dict, object].
One advantage is that indexing is already valid in type declarations, and its the typical syntax for parameterized types. Thoughts? Any other ideas?
I don't really like overloading [] even more, and I think () (or, perhaps, 'fused_type([list, dict, object])').
But I don't feel very strongly about it.
If you only want this allowed in typedefs, then, being puristic, I think that really a "fused type" is really different from a ctypedef, and that it would warrant something like a new keyword.
cdef fusedtype [list, dict, object] fused_t
That's rather horrible, but you get the gist. The thing is, once you use a ctypeudef, you really should allow
def f(fused_type(float, double) x, fused_type(float, double) y): ...
but then, how many fused types do you have, one or two?
Two, and you can't refer to them. Such anonymous types could be handy for one-off functions, e.g. def f(fused_type[list, dict, object] x): ... but maybe that's not needed.
So this makes it seem to me that using ctypedef is a rather horrible hack.
Yeah, this is the crux of the issue. (To be clear, Mark's implementation is good, it's our syntax that's hacky). It's perhaps less ugly than introducing a new keyword. A crazy idea: cdef fused floating_t: float double long double (in analogy with how we declare types like structs and enums).
But, like I said, I don't feel strongly about this.
P.S. Anyone remember buffers and C++ templated types are dissallowed as typedefs?
As for buffers I just think I never got around to it...
And in that case you can't just punt the typedef to C :). - Robert